---
prelude: >
    The ability to use non-Keystone authentication systems has been removed.
upgrade:
  - The ``--os-auth-system`` CLI option and ``OS_AUTH_SYSTEM`` environment
    variable usage was deprecated in the 3.1.0 release during the Mitaka
    development series. This release drops the support for using those options
    to load non-Keystone authentication systems via the
    ``openstack.client.auth_plugin`` extension point.
